Nitrilotriacetonitrile is produced by reacting an aqueous mixture of either ammonia or an equivalent ammonium salt, or hexamethylenetetramine with formdaldehyde and hydrogen cyanide in the presence of a strong mineral acid. Most nitrilotriacetonitrile has been produced at temperatures below 95.degree. C. At these temperatures, a concentrated reaction mixture exists as a dispersion of nitrilotriacetonitrile in water. Above 95.degree. C., nitrilotriacetonitrile and water form a homogeneous phase. Running the reaction above 95.degree. C. results in a reduced reaction time and can minimize difficulties in handling the dispersion. However, crystallization of the nitrilotriacetonitrile from reaction mixtures above 95.degree. C. has proven to be a problem.
When the reaction has been run at temperatures below 95.degree. C., the procedure has been to cool the reaction mixture rapidly in one step to 25.degree.-30.degree. C. This procedure has produced crystals that could be filtered and handled using normal production separation equipment. However, when reaction mixtures in excess of 95.degree. C. are rapidly cooled in one step to 25.degree. C. to 30.degree. C., the crystals produced are very small, are difficult to separate from the mother liquor and are difficult to wash, and can plug filters and lines. A crystallization process that produces large easily filterable crystals from nitrilotriacetonitrile reaction mixture when cooled from temperatures in excess of 95.degree. C. would be an advancement in the art.